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ACTH levels are normally highest in the early morning (between 6 and 8 A.M.) and lowest in the evening (between 6 and 11 P.M.). Therefore, a doctor who suspects abnormal levels looks for low ACTH in the morning and high ACTH in the evening.
The lipid bilayer is made of phospholipids. They are arranged in a double layer because one of their ends is attracted to water while the other is repelled by water.
Malaria was not eliminated in the United States until 1951. The term eliminated means that no new cases arise in a country for 3 years.
After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.